This multicenter, Phase 3 randomized placebo controlled trial is designed to determine whether the vertical HIV transmission rate can be reduced by continuous oral ZDV administration to HIV infected pregnant women between 14-34 weeks gestation, also giving an intrapartum intravenous dose and oral ZDV administration to their newborn infants from birth to six weeks of age. This study also designed to evaluate the safety of ZDV for both the pregnant woman and for the newborn infants.